1. Field of the Invention
This invention relates to the diagnosis of stroke by the measurement of unbound free fatty acids in body fluids such as whole blood, plasma and serum.
2. Description of the Related Art
Stroke is defined as the interruption of blood flow to brain tissue. This can be an interruption to a particular portion of the brain or a reduction of virtually all flow when, for example pumping of the blood by the heart fails completely. More frequently, stroke occurs when flow to a particular part of the brain is interrupted by the blockage or rupture of a blood vessel that serves the brain. Blockage of a vessel, for example, through an embolism or the formation of a thrombus, generally in an artery that supplies blood to the brain is known as an ischemic stroke. The rupture of a blood vessel within the brain, generally through an aneurysm, is known as a hemorrhagic stroke.
In the case of an ischemic stroke, the interruption of blood flow may be temporary; this is known as a transient ischemic event (TIA). In this case, the patient often suffers no clinically or measurable deleterious consequences but is at high risk for subsequent strokes. In contrast, patients whose blockage does not resolve within a few hours suffer permanent damage, often resulting in death. This is a consequence of the death of brain cells (tissue) that were normally supplied with nutrients and oxygen by the now occluded vessel. This death or infarct of the tissue can be detected by computer aided tomography (CT scan) or by nuclear magnetic resonance imaging (MRI) but only many hours after the stroke (the first symptoms) started. In the case of hemorrhage, the brain begins to fill with blood resulting in the destruction of tissue.
Stroke is the third leading cause of death in developed countries. New cases of stroke affect approximately 750,000 individuals every year in the United States alone. The estimated costs for treatment and lost productivity as a result of death and morbidity from stroke are about $40 billion dollars in the U.S. The only effective treatment available for stroke is the delivery of thrombolytic agents such as tissue plasminogen activator (t-PA) that destroy the clot by enzymatically cleaving proteins that help form the clot. T-PA can only be given within 3 hours of the first symptom because of deleterious effects (hemorrhage) if used too late. Moreover, t-PA can only be used in ischemic stroke; its use in hemorrhagic stroke generally leads to death.
Thus, thrombolytic therapy can only be used if diagnosed quickly and only if hemorrhagic stroke is ruled out. Current methods of diagnosis rely virtually entirely on clinical presentation, generally the opinion of the emergency physician. If the physician suspects stroke and thinks that the patient may be a candidate for thrombolytic therapy, then the patient must quickly undergo a CT scan to rule out hemorrhage (which the CT scan can detect at an early stage). Generally, because of the time required for these decisions and procedures, very few potentially eligible patients receive thrombolytic therapy.
Consequently, there is a long felt need for availability of a simple and rapid blood test that would determine the presence or absence of ischemic stroke in an individual and could distinguish between ischemic and hemorrhagic stroke. The diagnostic method described here, measurement of unbound free fatty acid in body fluids such as blood, serum or plasma, involves a simple, inexpensive, virtually instantaneous, and readily accessible measurement that has high potential for revealing the ischemic event.